1. Field of the Invention
The present invention relates to a flight control system for an aircraft, particularly for a helicopter.
Said flight control system is intended more particularly, although not exclusively, for facilitating ground approaches, for the purpose of landing, with a strong crosswind, in particular steep approaches in poor visibility.
2. Description of the Related Art
Usually, when a helicopter makes a so-called "instrument" approach, following a guidance direction (or approach path), for example a guidance beam emitted by a ground marker, it corrects the lateral deviations, for example the drift caused by a crosswind, by a course modification in the appropriate direction. It thus produces a lateral speed with respect to the ground, which allows it to return to the approach path if it deviates therefrom.
This usual mode of approach, by course modification, although widely used does have several drawbacks, especially in the case of aircraft, such as a helicopter or a tilt-rotor aircraft, which are capable of making steep approaches at low speed.
This is because, at low speed, which is necessary in the case of a steep approach, controlling the course by the roll become difficult since the slightest inclination generates a large yaw rotation.
In addition, compensation for a strong crosswind or correction of a drift generated especially by a strong crosswind relative to the approach path generally requires a very large course deviation with respect to the alignment with said approach path.
In practice, this course deviation sometimes amounts to values greater than 30.degree., something which is hardly acceptable, especially for safety reasons.
The object of the present invention, which relates to a suitable flight control system, is to remedy these drawbacks.